1. Field of the Invention
This invention relates to vehicular semi-automatic mechanical transmission systems and, in particular, to semi-automatic mechanical transmission systems of the type providing partially automatic implementation of a manually or automatically selected shifting of mechanical transmission gear ratios. Transmission systems of this type are disclosed in U.S. Pat. Nos. 5,053,961 and 5,053,962, both assigned to the assignee of this application, the disclosures of which are incorporated herein by reference. More particularly, the present invention relates to a semi-automated transmission system of the type described which is provided with an engine fuel controller controlled by the system control unit for causing synchronous conditions after manual fuel or clutch manipulation to initiate a shift sequence by causing a torque break.
2. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Such fully automatic change gear transmission systems include automated transmissions wherein pressurized fluid is utilized to frictionally engage one or more members to other members or to a ground to achieve a selected gear ratio as well as automated mechanical transmissions utilizing electronic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e. positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are hereby incorporated by reference.
Such fully automatic change gear transmissions can be unacceptably expensive, particularly for the largest heavy-duty vehicles which are not typically sold in high volumes. Additionally, those automatic change gear transmissions utilizing pressurized fluid and/or torque converters tend to be relatively inefficient in terms of power dissipated between the input and output shafts thereof.
Semi-automatic transmission systems utilizing electronic control units which sense throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior. Examples of such semi-automatic transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
While such semi-automatic mechanical transmission systems are very well received as they are somewhat less expensive than fully automatic transmission systems, allow manual clutch control for low speed operation and/or do not require automatic selection of the operating gear ratio, they may be too expensive for certain applications as a relatively large number of sensors and automatically controllable actuators, such as a master clutch and/or a fuel throttle device actuators, are required to be provided, installed and maintained.
A semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means, and a manually only controlled master clutch is disclosed in above-mentioned U.S. Patent Nos. 5,053,961 and 5,053,962. This system includes a control/display panel or console for operator selection of upshifts, downshifts or shifts into neutral, an electronic control unit (ECU) for receiving input signals indicative of transmission input and output shaft speeds and of manually selected shifts and for processing same in accordance with predetermined logic rules to issue command output signals and a transmission actuator for shifting the transmission in accordance with the command output signals.
The control/display device will allow the operator to select/preselect a shift into a higher ratio, a lower ratio or into neutral and preferably will display the selected but not yet implemented shift as well as the current status of the transmission. Preferable the control will also allow selection of operation in an automatic preselection mode of operation.
Accordingly, a control system/method for a vehicular semi-automatic mechanical transmission system for partially automatic implementation of driver and/or controller selected transmission shifts which did not require throttle or clutch actuators, and which required only two speed signal inputs, was provided. While this type of transmission system was well received, for certain situations to enhance ease of operation, especially for less skillful drivers, the lack of an automated engine fuel control to provide an automatic and accurate synchronizing function after initiation of the shift sequence was not totally satisfactory.